I'm not sure i'd agree with that but it depends on how well someone picks up software. Photoshop is not so complex really and it's got very low barriers to entry. You can open a photo and play around with the tools and get a very good handle on it. Pair this up with some good foundation tutorials and you'd be away. Because it's a mainly revolves around 2D image manipulation the tool analogies used within the program are very simple and therefore make sense very quickly.
Sure, if you have the time, patience and leisure to poke around, search for tutorials, read through books and learn by trial and error, otherwise you could get a good handle on the fundamentals and learn all of the basics listed below from a seasoned pro in a 6 hour crash course.
The Photoshop Environment: What does Photoshop do? Introducing pixels and selections. The navigator window: getting around in an image, zoom shortcuts. Using the history palette. Multiple undo and snapshots.
Image Basics: Resolution and file size. Different image formats and their uses. Colour types.
Selection Basics: The different selection tools. The magic wand and tolerance settings. Inverting selections. Feathering selections. Anti-aliasing. Expanding and contracting selections, transforming selections, adding to and subtracting from selections.
Adjusting Images: Working with Levels and Curves. Hue and saturation. The info palette.
Layers: Creating new layers and duplicate layers. Importing layers from other images. Giving layers transparency. Linking and merging layers
Channels: Adjusting individual channels. Saving and loading selections.
Saving Files: Adjusting image size. Changing colour type. Flattening layers. Cropping images.
The Painting Tools: Brush selection and adjustment. Colour selection. Creating new brushes. Using patterns. The other painting tools. The healing and clone stamp tools
Masks: Quick masks. Layer masks. The graduated fill tool. Editing gradient properties
The Pen Tool: Creating and editing paths. Generating clipping paths.
More About Layers: Adding layer effects. Creating and using layer sets. Clipping groups and their uses. Changing the hierarchy of layers.
Working with Type: Editing type. Colouring type. Distorting type Rasterizing type layers.
I guess it comes down to your overall objectives, learning style and time. If you are just interested in playing around with the tools and in no rush to learn all the basic fundamentals at once, then poking around the net and teaching yourself is a very viable option.